5 Replies Latest reply on Jan 23, 2009 6:45 PM by the chuck

    IIR or FIR type filters

    the chuck
      Is it possible to do IIR type filters via PixelBender? I'm thinking that it is not, because most IIR filters require the previous sample's result:

      Here is the standard Butterworth IIR filter equation for a 2-pole Lowpass Filter:
      y[n] = output
      x[n] = input
      aN = coefficient
      bN = coefficient

      y[n] = a0*x[n] + a1*x[n-1] + a2*x[n-2] - b1*y[n-1] - b2*y[n-2]

      As you can see, the filter requires the calculated output of the previous calculation in order to compute the current output.

      in PixelBender, this would be like saying:
      Output[25] = a0*input[25] + a1*input[24] + a2*input[23] - b1*Output[24] - b2*Output[23].

      I'm hoping this is wrong, but there is no way for pixelBender to see a calculated pixel and use it to calculate a separate pixel, correct?

      I'll have to look for a Finite Impulse Response 2pole lowpass filter if there is no way around this, as they don't require already calculated data as part of the input.